1. Field of the Invention
This invention relates generally to storable cement slurries and, more specifically, to suspending agents for storable cement slurry systems. In particular, this invention relates to iota-carrageenan suspending agents for storable cement slurry systems, such as those employed in cementing wells penetrating subterranean formations.
2. Description of Related Art
Conventional cement slurries set and develop compressive strength due to hydration. Such cement slurries are commonly used for cementing operations in subterranean well applications. For example, cement slurries may be used to cement a casing string into a borehole or to cement a pipe string, such as a liner, within another casing string. Other applications include, but are not limited to, squeeze cementing of casing perforations, liner tops, casing leaks and other remedial cement applications.
Typical cement slurries used for well cementing operations are formulated and mixed on-site using relatively complex and expensive mixing equipment. Because these cement slurries typically set quickly, they cannot be made in advance. Rather, cementing equipment and personnel are usually required to standby on location until the time for commencing cementing operations. Accordingly, any delay in drilling or workover operations during this standby time results in increased expenditure and lost time for cementing equipment and personnel.
In an attempt to address the problems associated with delays, storable cement slurries have been developed that may be mixed and stored in advance. These storable slurries may be made up in nonpressurized vessels at a location removed from the wellsite, then transported in liquid form to the wellsite and activated when ready to use. Such storable cement slurries are described in U.S. Pat. Nos. 5,447,197 and 5,547,506, which are incorporated herein by reference in their entirety.
Although previous storable cement slurries partially address the problems associated with on-site cement mixing operations, some suspending agents typically employed with these previous systems may not provide sufficient suspension time for some applications. In addition, some suspending agents potentially employed with these systems, such as polyethylene oxide, may be incompatible with other cement additives. In addition, some suspending agents typically employed with these previous storable cement systems may not provide sufficient suspension time for some applications.